This invention relates to a positioning device for positioning an engine bonnet or a boot lid of a motor vehicle. Such positioning devices are commonly in use and comprise primarily a gas spring, which gas spring assists a lifting movement of the respective engine bonnet or boot lid. Alternatively, the gas spring is replaced by a so-called oil support, which is also a cylinder piston device and has a primary function of maintaining the engine bonnet or boot lid in a raised position. Frequently, the gas spring or oil support has only a limited stroke, such that the bonnet or boot lid can only be positioned in a normal opening position which is sufficient for normal loading of the luggage space of the motor vehicle and for performing normal service steps at the engine. Sometimes it is necessary, however, to open the engine bonnet or boot lid beyond said normal opening position, e. g. if the engine is to be removed from the motor vehicle. For allowing such further opened position of the boot lid or engine bonnet, it is known to provide a telescopic tube on the cylinder of the gas spring or oil support. This telescopic tube can be moved with respect to the cylinder and locked with respect to the cylinder in a position corresponding to said further opened position of the engine bonnet or boot lid.